I have "bad knees" and have to avoid any sort of high-impact workout. What can I do to keep myself aerobically fit?

--carol

Welcome to the club, Carol! Loads of us have cranky knees from too much running, high-impact aerobics, and the sporting life in general.

Cycling is still my first choice for low-impact aerobic exercise. If I can't get outside on my bike, I can do it indoors in a gym. I even take a bike with me on some vacations and get my exercise in while seeing the sights.

Another great non-impact exercise is cross-country skiing. Of course if you don't have snow, you'll need access to a NordicTrack ski machine. Or you can always try swimming, which is the gentlest exercise in terms of kindness to body joints. It's also one of the few great upper body aerobic exercises.

Some gyms have upper body ergometers (UBE) -- a contraption where you crank your arms for a cardiovascular workout. You'll get a hell of a pump after 20 minutes on a UBE.

You can also strengthen the muscles surrounding the knee. Quads and hamstrings are the muscles that flex and extend your knees and leg extensions and leg curls will strengthen these right up.

In time, you may get to the point where you can play tennis or ski without undue discomfort. Or, you may never reach this point. (Sorry to be the bearer of potentially bad news.) Just make sure you check with your doctor before participating in any sort of questionable activity.